The Physiology of Fitness
Responses to acute exercise
The musculoskeletal system consists of muscles, bones, joints, tendons and ligaments; it is the muscular and skeletal system combined. Before you exercise, you need to warm up as this prepares the body for different movement in activities and it reduces the risk of injury. Then you carry out mobilisation activities which increase the joint mobility; it enables the joints to become more lubricated by releasing more synovial fluid onto them.
Increased blood supply
There is a continuous circulation of blood in the body. It transports oxygen, carbon dioxide, nutrients, hormones and metabolic waste around the body. During exercise, when your body works 'overtime' your heart rate increases so more blood is needed within the muscles. When our heart rate increases it enables oxygen-rich blood to be pumped around the body at a faster rate which warms our muscles and helps to deliver more oxygen to the working muscles. There is a bigger demand for oxygen because the muscles are working more than usual so they need more energy. The blood from other body parts such as organs is reduced. This is known as 'redistribution'. The blood vessels in your muscles dilate and the blood flows around the body at a faster rate because of the bigger oxygen demand. The ATP gets used up in the working muscle producing several metabolic byproducts such as adenosine, hydrogen ions and CO2 which leaves and causes capillaries in the muscle to dilate (expand). This increase in blood supply allows for more waste products to be carried away from the working muscles, therefore it helps to reduce the build up of lactic acid.
Increase in muscle pliability
The muscle spindles that are located within muscle fibres stretch when nerve impulses are made and the information for the degree of the stretch is sent to the nervous system. As the tissues warm up, the rate of nervous impulses also increase and so does the speed of the nervous transmission.
When you exercise, more blood is pumped through the muscles as excess heat is generated so the muscle tissue warms up. The muscles become more pliable which means they are able to change shape more easily. So, they can adjust and are flexible. The msucles adjust so that the lactic acid present in the muscles clears up; by doing this they can become more pliable to different movements. This allows you to stretch to greater lengths without tearing muscles and decreases the risk of getting muscle strains. For example, Plasticine pulls apart when it is cold and stretches when it's warm just like muscles.
I recorded my flexibility with the sit and reach test before exercise and I got 30cm. Then during exercise I got 30cm, then I got 31cm after exercise. This shows that the muscles became more pliable once they had warned up after exercise.
Increased range of movement
The bones in the body are help together by joints which allow movement between them. The degree of the joint movement is known as the range of motion. Doing exercise means our joints are moving quickly so there needs to be more synovial fluid in the joints to allow this movement. The joints become warmer as exercise increases the body temperature and the synovial fluid becomes thinner, making the movement more efficient. To achieve a full range of movement you need to start doing small movements and gradually get larger until a full range of movement is reached. If you have increased muscle pliability then it will allow for a wider range of movement and reduce the risk of any injuries. The range of movement and mobility of the joints increases due to the synovial fluid being thinner and warmer, which causes an increased elasticity of tendons and ligaments. The joints that need to be mobilised are: Shoulders, elbows, spine, hips, knees and ankles.
Muscle fibre micro tears
Every muscle in the body is made up of thousands of fibres which pull against each other. There are microfilaments (actin, myosin) found in muscle cells that enable it to contract. Depending on the intensity and duration of the exercise you are doing, you could feel aching in your muscles. There are more fibres that are involved in contracitons when you exercise so they are stronger and it meand that you have less opportunity to rest. During resistance exercise, the muscle fibre 'breaks' which are called micro-tears or micro-trauma as the damage is minimal. This happens when muscles are put under excessive stress such as lifting weights. The myosin heads and the actin filaments are pulled from the myofibrils as the muscles are liftings weights that they can't hold. The damage causes a release of chemicals that cause mild to moderate soreness and stiffness. If it lasts a few hours or hurts the day after, it is referred to as DOMS which is delayed onset muscle soreness. Other pains resulting from intense exercise are aching, fatigue and a limited range of movement. During rest from training/exercise, if any damage has occured then the muscle will react by adding proteins and the chemicals stimulate growth and repair in the area. So, it rebuilds becoming bigger and stronger over time. This process is called muscle hypertrophy.
Energy System Responses
Lactic acid System
The Energy Continuum
The energy continuum is the term used to describe the types of energy systems used during physical activities. The energy systems all work together and what we do determines which energy system supplies the majority of ATP. The energy continuum highlights which system produces the most amount of energy at different stages of an activity. More ATP is needed when we do exercise so we use the phosphocreatine system for short bursts of energy like during a 100m sprint and the lactic acid system when the PC stores run out. But when we rest, all of our energy is supplied by the aerobic system. We also use this system during long periods of exercise like a marathon. Some sports need all three energy systems, for example, football because the intensity varies from low to very high. Our body uses the food we have eaten, converted by energy systems to produce energy. Different sports have different energy requirements.
Heart rate anticipatory Response
I recorded my heart rate before exercise and it was 65 beats per minute, then during exercise it was 127 beats per minute and after exercise it was 90 beats per minute. This shows that it increased due to the exercise but afterwards it slowly started to decrease.
Increased blood pressure
When we exercise, our blood pressure increases which is needed for the blood to flow around the body quicker. The contraction of the heart produces this blood pressure as it pushes blood into the blood vessels. The heart contracts faster as the heart rate increases which leads to an increased blood pressure. When your blood pressure is taken, two values are given: Systolic (when the heart is contracting) and Diastolic (when the heart is relaxing). When you rest, a healthy individual should have a blood pressure ranging from 110-140mmHg for systolic and 60-90mmHg for diastolic. During exercise, the systolic should increase to 200mmHg- 250mmHg for healthy exercise and the diastolic shouldn't hardly change even if you are exercising. It can decrease because of the dilated blood vessels in the working muscles that let heat escape. If it increases by 15mmHg it could indicate that you have coronary heart disease.
Vasoconstriction and Vasodilation
Increase in breathing rate
The number of breaths per minute increases due to neural and chemical influences. The rate and depth of breathing is controlled by the respiratory centre located in the Medulla (brain stem) which sends neural impulses to the respiratory muscles. Also, chemoreceptors are located around the body but mainly in the bigger blood vessels like the aorta. These are sensitive to chemicals such as O2, CO2 and pH levels within the blood. If they detect a change in normal levels, they stimulate the body to remove them by increased breathing.
Pulmonary ventilation is the amount of air we breathe in and out per minute (VE). It is worked out by the frequency x tidal volume (Breaths per minute x volume of air in one breath). The average breathing rate is 12 per minute, the average tidal volume is 0.5 and the average VE is 12 x 0.5 =6 litres.
I recorded by breathing rate before exercise which was 18 per minute, then during exercise it was 38 but then it dropped to 22 after exercise. This shows an increase in the breathing rate when exercising but it starts to lower when you start to exercise.